Sonic system for augmenting the extraction of oil from oil bearing strata



Feb. 2, 1954 A GIBODIN E, JR SONIC SYSTEM FOR AUGMENTING THE EXTRACTION OF OIL FROM OIL BEARING STRATA Filed Feb., 17, 1948 3 Sheets-Sheet 1 IIIIIIIIIIIIIIIIIIIIIIIllIIlIlIII/Illlllllh 'IIIIIIIIIIIIIIIIIIIII'IIII; w

Iva-Mme A. G. BODINE, JR SONIC SYSTEM FOR AUGMENTING THE EXTRACTION Feb. 2, 1954 OF OIL FROM OIL BEARING STRATA 3 Sheets-Sheet 2 Filed Feb. 17, 1948 firm me. W13 5 A. GJBODINE, JR 2,667,932 SONIC SYSTEM FOR AUGMENTING THE EXTRACTION mus swam Feb. 2, 1954 OF OIL FROM on. BE

3 Sheets-Sheet 3 Filed Feb. 17, 1948 [WM/Pine mat/25mg.

7 vl w\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\ Patented Feb. 2, 1954 UNITED STATES PATENT 2,667,932 OFF ICE SONIC SYSTEM FOR AUGMENTING THE EXTRACTION OF OIL FROM OIL BEAR- lNG STRATA 7 Claims.

1 This invention relates generally to systems for increasing the flow of Wells, particularly though not necessarily oil Wells, and deals more especially with a system for increasing the flow' from the oil bearing strata to the well by application to the strata of elastic waves of sonic character, i. e., waves traveling in the strata at the speed of sound. The present application is a continuation-in-part of my prior application entitled Method and Apparatus for Treating Wells, filed May 14, 1941, Serial No. 393,352, new Reissue Patent No. 23,381; and is also a continuation-in-part of my prior application entitled Method and Apparatus for Pumping, Serial No. 761,456, filed July 17, 1947, now Patent No. 2,444,912, which application is a continuation-inpart of my original application of the same title, Serial No. 521,576, filed February 8, 1944. The present application is also a continuation-in-part of my prior application entitled Method and Apparatus for Boundary Layer Control, Serial No. 771,808, filed September 2, 1947, now abandoned.

It is a well known fact that the Nation currently faces a serious petroleum shortage. It is a further known fact that, when an oil Well is abandoned for lack of further economical production, more than two-thirds of the oil reserve is still in the ground. In other words, speaking generally, it has, to date, been economically feasible to extract an average of not over about one-third of the potential total recovery from known fields. It need hardly be said that any means for increasing the percentage of recovery would be of extreme value.

It is accordingly the major object of the present invention to provide a system for augmenting the flow from the strata to the well, to the end that a higher percentage of recovery of the total fiuid in reserve in the formation may be achieved.

I have found that the rate of migration of oil through wet sandstone can be increased 50% by applying sound waves vto the sandstone. By sound or sonic waves, I mean waves of elastic deformation propagated in the formation at the speed of sound, and not necessarily waves limited to the frequency range of human hearing ability. In the transmission of sound waves through an elastic medium, such as a stratum of sandstone, the movement of the individual particles of the medium is purely local, each particle making small to and fro excursions in a manner similar to the vibrating body generating the waves. The particles move largely in the same line as the directions of propagation of thewave, but with only a very small ampliture of travel or displacement.

My invention contemplates the utilization of such movement of the particles in response to sound waves for the accomplishment of a fiow of fluid through the porous oil bearing earthen formation adjacent to an oil well. This I usually accomplish by establishing within the medium transmitting the sound waves a resonant condition in which a large part of the energy supplied by the generating vibrator is stored. in the medium by the reflection of the sound waves in such a manner as to reinforce these originating with the generating vibrator to establish within the medium a standing wave. This reinforcement by reflection continues, and increasesthe amplitude of the standing wave.

The invention is made more effective by the fact that sound waves properly applied directly to an oil bearing stratum will be confined thereto, and not dissipated in adjacent non-bearing earthen strata, because of the substantial difference in acoustic impedance as compared with adjacent strata. Thus, waves are found to be reflected at the boundaries of the oil-bearing stratum and so confined against dissipation outside. The energy transmitted to the oil bearing stratum is accordingly kept within the stratum, resonance may be established therein, as mentioned in the preceding paragraph, and the oil bearing structure thus made to absorb a very substantial quantity of wave energy.

It is beyond the scope of this disclosure to theorize all of the reasons why the invention is effective. However, the following factors are apparent:

Sound waves traveling in an elastic medium are subject to attenuation, the lost energy of the Wave being converted into heat. Heat generates gas pressure, as well as reducing the viscosity of the oil, and hence oil migration must be increased.

Oil is trapped in earthen formations by water filaments bridging the gaps between sand particles. Periodic acceleration of the formation by transmitting sound waves therethrough causes or permits the oil droplets to puncture these water filaments, and so to become freed for migration.

Oil exhibits boundary layer adhesion to the surfaces of the sandstone, which seriously impedes the flow of the oil to the well, but which can be materially reduced by transmitting sound Waves through the sandstone, the oil or both. Such waves act to reduce the frictional drag of the formation on the well fluid by agitating, breaking up and scrubbing away the boundary layers of the fluid which are otherwise bound adhesively to the formation.

Whether or not the above factors are exhaustive of the flow promoting conditions established by the invention, is a question beyond present knowledge. Sufice it to say at this time that I have found sound waves applied to an oil bearing earthen formation to materially augment the flow rate therethrough.

The broad invention consists of a system of di rect application of sound waves to an oil bearing stratum to augment the flow rate through the formation to the well, and the percentage of ultimate recovery of the total reserve present in the stratum.

The itxiiiion further includes methods and apparatus of various classes for applying the;

sound waves to the producing structure. The

invention is applicable both lto pumping;Qwells and flowing wells. It is also -'Wi-t'hinthe capabilities of the invention to transmit sound waves from the region immediately adjacent, onewell to regions adjacent other wells and thus to augment the flow rate from a groupbf wells in the formation, though using but a singlewellas asource of waves. Further, I may employ an abandonedweH asagpowerful source of sound esi'byj,installing -liigh, power sound wave gen- .eratingfapparatus therein, with no revived proiduciti'on. from that, particular well attempted. LThehi'gh'lenergy Waves transmitted into the for- .m 't'ion fromjthehigh power apparatus thus in- "fs'talle'd are propagated for a considerable distancefthrough the stratum, and may thus revive "wells over a substantial field area.

,Sincewell casings'are perforated in the region .ofjproducing' structure, it is very often sufficient to'japply "the waves" to the fluid inside the well. I,l'1isfsonic wave'energy is radiated through the j'perforations directly into the producing forma- ,ti'ons, In some instances I prefer to increase the ntact the perforations to increase wave trans- "I'ni'ssion' efficiency.

jfVariousadditional objects and features of the invention in its several illustrative forms will be niade'a'pparent' in the course of the following destalled description of several present embodijffnent'slthereof selected for illustrative purposes. ,ilflor this purpose, reference is directed to the accompanying drawings, in which:

Figure l'is a longitudinal sectional view, part- Jlyjin elevation, showing one embodiment of the "invention; 7

Figure 2 is a somewhat diagrammatic view showing, a simplified form of the invention and i'sl iowingalso afstanding wave pattern;

Figure 3 is a longitudinal sectional View, partly ineleyation, showing another modification of the invention; I

Figure ,4 is another view partly in longitudinal 'sectionand partly in elevation showing another embodiment of the invention; and- I "Figure 5 is a view, partly in longitudinal sec- "tionfand partly, in ,elevation, showing another embodiment of the'invention.

The process of the present invention, a in one, ,general aspect, involves and depends upon'several important steps, viz: generating high energy sound Waves, efiiciently transmitting saidwaves to the productive formation, and effecting an eliicient energy transfer. between the transmission means and the formation. Several distinct forms of apparatus in accordance with the inventionfor accomplishing this process are disclosed herein, and the process invention may most con- '"veniently be understood froma consideration of these several forms of apparatus as employed in j different illustrative applications'of the invention,

Referring first to the application of my invention illustrated in Figures 1 and 2 wherein sound ,W'ave generating apparatus is installed in an abandoned oil well (or earth bore not to be used as a producing well), numeral l8 designates well Q casing sunk in bore 1 I, to theregion of oil productive stratum l2.

Such casings may originally have extended to the bottom of the bore, but

forpresentpurposes is preferably cut off near the top of the"oil-bearing stratum l2, as indicated.

An elastic compression column MQcoin'poSed of a good grade of elastic steel, is suspended within casing Iii, and has mounted on its upper end sound wave generator l5, one embodiment of which is' -td described in more particular here- 5 inaf ter. slelastic column I4 is of sufficient diameter for'its length to transmit longitudinal elastic waves of compression, and by use of the eirpr essionfcompression column I have ref- .erenceto this is'tifiness characteristic. Near 10 the-supper end of column I l, the column is furnished with an enlarged head or collar I6. he co umn 5 ts i Te a tu 1 f rm in a horizontal top plate [8, the head overhangi san a i id wn a d o we la r n 15 aperture llfor thesupport of the column, Vertically spaced below top plate 13 is a horizontal Qbottom or baseplate carried by tubular member and fiange22 bolted to casing headlflange 23. Between base plate 20 and top plate l8 are 20 a plurality of coil springs 24, positioned on vertical pins 25 set tightly into base plateiil and projectingwith working clearance through bores 26 in top plate l 8. The weight of the column 14 is thus transferred to springs 25, and thence to 5 the casing I ll supported by the earth.

V A body of cementZl is filled in the well bore around the. lower portion of thecolumn. If desired, the column may be grooved as at 23 toleey the columnto the cementbody and thus'assure so vib at em v men o t l h the col mn- Alternative1y,.a bodyof packed wet sand maybe used in place of the cement, This .body of cement or sand, as thecase may be, places theelastic column in solidto-solid engagement with the formation, thusproviding 'good 'wave energy transmission between the column and thesurrounding formation, as more fully described here- Sound wave generator'IB comprises a housing 40 30 containing ameans for settingup vertically directed vibrationsand thereby exerting a vertical oscillating force upon the upper endofthe column I4, The Imeans for generating these vibrations may be inechanical, electrical, hydrauhe or any other type capableuofv delivering suffi- ,cient, power A type'of generator well adapted f'orthc', p rpose has meshing oppositely rotating gears 3|, carrying eccentric weights 32 which balance out,horizontalvibrations but cause vertical,vibrationsto be additive to produce a substantial resonant oscillatory force in a vertical direction. 'Ihedriving pulley 33 of the sound Wave generator, mounted on the shaft for one of the spur gears, is driven by an electric'motor or anyother suitable prime mover (not shown) through belt 36.

In a simplified embodiment ofthe invention, the column 14 may'con'sistjof a steel column of substantiallyuniform, diameter from the gen- 50 erator {5 to its lov'ver endu Such an embodiment &is somewhat diagrammatically represented [in Figure 2, togetherwitha typical standing wave patterntherefor. ,Forjsimplicity, the operation ofthe apparatuspfl Figure ,1 will first be de- 5 scribed with the [assumption that the column, [4

, is actually of uniform diameter from top to bottom. r

Generator l5 applies, an oscillating force in a vertical-direction to the, ,upper end of, elastic 701.colu'mn l4, thereby launching alternating elastic deformation waves of,tension, and compression .,.in,.a longitudinal L direction 1 down the column,

j 's'ad waves tra elingin theelasticLcolumn with 'transmission; ofhelastic anelastic column" is a well understood phenomenon usually treated of in works on acoustics under the heading of longitudinal vibrations of rods and need not be explained in great detail herein. It should, however, be understood that longitudinal elastic waves in an elastic column cause sections of the rod to oscillate longitudinally of the column, with a displacement amplitude depending upon the energy of the wave and the longitudinal stiffness of the column.

The column [4 is usually long relative to a wave length measured along the column. Waves in the approximate frequency range of to 30 cycles per second appear to give the desired high amplitude waves capable of traveling long distances in the formation, e. g., hundreds of feet. A cycle wave has a wave length in the column of the order of 800 feet, and the column may hence be several wave lengths (fundamental frequency) long for a typical oil well installation. Various harmonics, of lesser wave lengths, may also appear.

It will of course be clear that the wave frequency is determined by the speed of the sound wave generator l5, and that by varying the speed of the latter, all or any of the desired ranges of frequencies may be employed. The vibration amplitude of the generator will of course depend upon its frequency, and it is found that a moderately low sonic frequency, as 10 to 30 cycles, affords the necessary vibration amplitude for equipment of the type herein disclosed.

For eflicient transmission of the wave energy from the generator down the elastic column, the generator should be adjusted to a resonant frequency of the column, so as to establish a standing wave along the column, as represented in Figure 2, this being accomplished in the case of a column with free ends, by adjusting the speed of the generator to produce such a wave length along the column that the column length is equal to an even number of quarter wave lengths. The standing wave results from interference of waves reflected by the ends of the column with the generated wave, as is well understood in the art of acoustics. In an actual installation the lower end is not entirely free because it is reactively connected to the formation so that the latter becomes part of the resonant circuit. Nevertheless, good reflections of waves occur at the lower end. The conventional standing wave diagram to the right of the column in Figure 2 represents the envelope of vibration mation. Good coupling and good energy transfer to the earthen foundation is desired especially in the more powerful forms of my invention, such as those employing steel columns, because large amounts of energy can be transmitted without over-stressing the steel if the energy is rapidly transmitted from the bottom to prevent excessive resonant amplitude. Such energy transfer depends upon the provision of a good impedance match between the column and the formation, which is accomplished by the use of a column having heavy mass and large area in contact with the formation, or with the cement body, which is inturn a heavy body of large surface in contact with the formation. In the case of a filled-in body of packed sand, such body is very tightly packed under the high pressure involved, and becomes, in effect, a part of the formation. A determination of the weight of the bottom end portion of the column in engagement with the formation is also governed by the frictional resistance to its reciprocation and by the resistance to its movement offered by the material in contact therewith, or with the cement body in which it is embedded. The bottom end column portion (section 42 of Figure 1) must be made of sufiicient weight that its efficiency as an energy transmitting member is not overcome by the inertia and other resistance to motion of its environment, which, if the column is very light, may serve to damp out entirely its movement and render negligible the wave energy transmitted thereby.

In operation, elastic waves generated at the top of the column are transmitted down the column as periodic alternating waves of tension amplitude at various sections along the column,

assuming moderate reactance at the lower end, and it will be observed that the upper and lower end sections of the column, as well as sections spaced by a half-wave from the column ends, experience substantially maximum vibration amplitude, while sections midway therebetween experience zero or minimum amplitude. The terms velocity anti-node and velocity node are conventionally applied to the maximum and zero amplitude regionsof the standing wave, as indicated at V and V, respectively, in Figure 2. Such resonant standing wave conditions assure optimum power transmission from the generator down the column to the body of cement 21, and thence to the formation.

The use of a vibration generator l5 characterized by simple harmonic motion is of substantial importance, since such a generator generates sound waves permitting the application of accoustic methods to accomplish good energy transfer between the steel column and the forand compression, the waves preferably being generated at a resonant frequency of the column, all as already explained. These waves setthe lower end portion of the column into vertical oscillation, from which the wave energy is transmitted to the cement body 21, and thence to the surrounding earth formation in which the cement body is embedded. The wave energy so delivered to the elastic earth formation travels radially outward in the latter with the speed of sound. These elastic waves traveling in the oil bearing stratum I2 are reflected at the boundaries thereof by reason of the substantial difference in impedance usually encountered in twoadjacent strata.

With high energy waves of steep wave front such as may be transferred to the earth formation with the apparatus of Figure 1, the wave action is effective for hundreds of feet to augment the flow rate through the earthen formation by reason of heating, removal or reduction of the adhesive boundary layer on the surfaces within the interstices of the formation, and memoval or puncture of internal flow-impeding water filaments in the formation.

The specific elastic column M of Figure 1 is made up of several sections 40, 4| and 42 of increasing cross-sectional area and massiveness in a downward direction, the bottom section 42 be-,

ing for example 7%" in diameter, and about long. The increasing cross-section causes an increase in longitudinal dynamic stiffness, which results in turn in reduced amplitudeof vertical oscillation. The reduction in amplitude of 0scillation, however, is accompaniedvby a corresponding increase in the forcewith which the columnv moves. The tapered column thus functions as an acousticlever, transforming the wave energy delivered by the generator to a higher impedance state characterized by reducedthese parts are conventional, but the vibration generator at the ground surface is shown, together with an upper end portion of the elastic vibration transmitting column. In this embodiment there is secured to the lower end of an elastic column III, which preferably may be a string of elastic sucker rod sections IIIa, I12, and I I I of progressively increasing cross-section in a downward direction, a massive bodyII2. Milled into the sides and bottom of this body are slots H3 in which are received anchor shoes H4 pivotally mounted on pins H5 set into the body H2. The shoes H4, shown in expanded position in the full lines of the drawing, are provided with casing engaging serrations II'I adapted to engage and grip the casing, the shoes being moved to expanded position by coil springs II8 placed between the shoes and the body, as indicated. In the expanded, casing gripping position, the anchor shoes extend angularly downward and outward from their pivot mountings on the body so that the weight of the body H2 and column I I I, or a portion thereof, if imposed on the expanded shoes in engagement with the casing, will cause the serrations to bite into the casing.

The shoes H4 may be retained in retracted position during installation in any suitable manner. For instance, they may be initially secured down against expansive springs I I8 by a shear wire I I9 adapted to be sheared by a small weight I23 movable in a central body cavity I 2I through which the wire I I9 is caused to pass by way of apertures I22. Transmission of vibratory energy down the column III in the manner presently to be described will vibrate the weight I20 against the wire H9 and cause it to fatigue and break, whereupon the anchor shoes are expanded by the springs and grip the casing.

The weight of the body II2 together with a portion of the weight of the column III) is permitted to be assumed by the casing, causing an elastic deformation of the casing in a downward direction. Of course the casing will part if too heavily loaded, so care must be exercised that only enough loading be transferred to the casing to give it the desired elastic deformation.

A sonic frequency vibration generator I25 at the ground surface is operatively connected to the upper end of the elastic column III. This generator I25 in this instance comprises an electric motor I26 whose shaft I21 operates an eccentric I 28 in the strap I 29 of a connecting rod I33. The rod I 36 is pivotally connected at I3I to an intermediate point I32 of a lever I33, one end of which has a pivotal mounting I34 on frame bracket I35 of motor I 26, and the other end of which is pivotally connected to the upper end of column II I. It will be seen that rotation of motor I26 will result in connecting rod I30 being driven to oscillate lever I33, and thereby reciprocate the upper endof column II I through a short vertical displacement distance. This movement of the upper end of column launches alternating elastic waves of compression and tension down the column, causing the lower end portion thereof, and the body H2, to oscillate vertically at the frequency of the generator I25. This oscillation is transmitted via shoes II4 to the casing, causing the whole lower end region of the latter to participate in the oscillation. The casing acts as a spring supporting part of the load of body H2, thus oscillatin locally in unison therewith. It must be understood that in all ordinary situations the column III will not 10 be bodily reciprocated, the wave lengths of the waves transmitted in the column being much shorter than the column length. In accordance with well known principles of vibrations in rods, different portions of the column may be moving in opposite directions owing to the progress of the wave action down the column. I

Preferably, to assure maximum powertransmission down the column, the wave generator I25 is operated at a resonant frequency of the column, so as to establish a standing wave therealong, which may be generally similar to that diagrammed in Figure 2, having a velocity antinode at the top, a velocity anti-node at the bottom (where the engagement is made with the casing), and a number of half-wave spaced velocity anti-nodes between. The mass of the body H2 at the lower end of the column III will have a reduced amplitude of oscillation because of the increased longitudinal dynamic stiffness of the column sections III!) and I I I0, and also because of its own ample acoustic impedance, but this reduction is accompanied by a desirable increase in force such as is necessary to oscillate the casing and to transmit substantial wave energy to the formation outside.

As already partially described, the suspension of the column from the lever I33 is so adjusted that a portion of the column weight along with the weight of the body II2 will be transferred to the casing, thus imposing a net bias on the casing causing an elastic deformation thereof. If the wave amplitude of cyclic displacement of the body II2 as driven by the column III is less than the supporting biasdeformation of the casing the latter will oscillate in step with the body H2. The elastic wave energy is transmitted from the casing to and into the formation by direct contact therewith.

Figure 5 shows an embodiment of my invention similar to subject matter first disclosed in my aforesaid application Serial No. 761,456. In said figure, numeral I36 designates the perforated casing in the well bore, and I 31 an elastic steel pump tubing suspended therein from coil type springs I38, the upper end of said tubing delivering well fluid to pipe I33. A sonic wave vibration generator I46, like the generator of Figure 1, is mounted on the top end of the tubing.

A check valve seat ring MI is tightly mounted in the tubing, near the lower end thereof, and is provided with check valve ball I42, while the lower end of the tubing is flared out laterally, nearly to the diameter of the casing, as indicated at I44.

In operation, generator I40 transmits elastic waves of tension and compression down the pump tubing, causing the lower end portion thereof (including not only the flare I44 but the ring I4!) to be longitudinally reciprocated through a short displacement distance at the frequency of operation of the generator I40, this action, and the preferred establishment of resonance in the tubing, are fully discussed in my application Serial No. 761,457. Each down stroke of seat ring I4! with the tubing occurs at an acceleration greater than gravity, and the check valve ball accordingly unseats during such time. Fluid displaced by the downwardly traveling seat ring therefore flows up through said ring; and fills the void above the ring caused by the down stroke of the latter. On the upstroke of the ring, the check valve ball seats, and. the column "of-fluid thereabove is elevated.

The flared lower end of the vertically oscillatvingpump.tubing, working withrelatively close ing oil bearing formation.

Itshouldbe notedthat many or. all of the embodiments of pump. disclosed in my applicationzSerial No. 761,457 willafford some coupling with thewellfiuid, but that in all cases excepting Figures. and .6 of. said prior application, the degreev of coupling is entirely negligible, and sound waves would not in practice .be radiated as far as. the oil'bearing formation. outside the casing. For example, the. end area-.of the pump tubing in the embodiment of Figure 4, or the end area of any of the pistons used with the embodiment of Figure 20, would bean insumcient fraction of. the cross-sectional area. of the casing for any effective wave transmission coupling to the external well fluid to be expected. The insignificant amount of. fluid moved by these areas on each. down stroke thereof simply escapes by moving radially out of the way and then up in the large annular space betweenthe pump tubing and. the casing, with exceedingly poor coupling efliciency. By having thepumping member nearly fill the casing, however, as does the flared type of tubing end, a substantial quantity of fluid is positively driven,.as.by a piston in.a cylinder, and suificient'wave energyistransferred to the well fluid to be radiated outinto the formation.

The variousembodiments of. my inventionall operate by establishment in .the. oil bearing stratum of. strong Waves. of. elastic. deformation. As. already pointed out, these. waves may operate in various ways to increase the. flow rate inthe formation, including heating, destruction of boundary layer adhesions, and puncture of water fil'ms or filaments- The heating. effect is useful not only in the earthenformation, but, in some forms'of my inventionwithin the well itself. Forinstance, in the. flowing. well installation of Figure 3, the heating effect. occurs throughout the entire oil column as. well as in the. formation, andhence serves to. reduce the viscosity of, the oil in the column, with inevitable increase in production rate. 7 It must be understood that themethod and apparatus of the.- .present. invention are characterized by continuous operation over longperiods of time,.with large energy transfer to. the formation. While all the factors involved are not yet known, it appears necessary that. operation. be sustained over time. intervals of the order of. days to secure thedesired results. Referenceis'here. made to my continuation-inpart application entitled Method and Apparatus for Augmenting the Flow of Oil From Pumped Wells, Serial -No. 50,428, filed July '23, 19.48, in which is. disclosed .and specifically claimed the subjectmatter of Figure. 5. hereof.v

Various illustrative embodiments of my invention have now. been described- Itis: of course to berunderstoodthat. these are. not to be regarded asthe only formsw-hich the invention can take in. practice, and that they invention is to be -limited only accordance with thelanguageof the following claims.

I claim:

L. For useinasystem for reducing; the clog,-

ging of. oil :tlow passages .in..a .produotion well or in theoil bearingiormation therearound ina production .oil .field which. system .has. an elastic sound wave generator atthe. ground surface adapted to set up elastic wavesin a wave transmissionmediumin a ,wel1 .ho1e in said field, the improvement comprising a wave transmission mediuminthe. form of astifi elastic compression column extending downthe well hole,.acoustically coupled to -the wave generator at the round surface, andracoustically coupled to the oil bearing. formation. atthe bottom, saidcompression column transmittingalternating elastic waves .of compression and tensionfrom said generator. into said oilbearing. formation to be expended therein.

2. The subjectmatter. of claim 1,.whereinthe acoustic coupling between the columnand the formationcomprises a packing of granular particles. between the. lower end'portion of the column and theformation.

3. The subject .matterof claiml, whereinsaid column, has near its lower end a surface set or packed. in a solid material in engagement with an uncased area oftheoilfbearing formation.

4. The subject matter of claim 1, wherein said compression column comprises a plurality of rod sections of. progressively. increasing cross-sectionalarea in a downward direction.

5'. In an apparatusforuse. in reducing the cloggingof oil flow passagesina production well or inthe oil bearing formation: therearound'in a production .oil. field, the. combinationofasolid elastic compressioncolumn, capable of transmitting elastic waves of. both tension and compression, positioned'in the well hole, a vibration genorator mounted on the top of. said com-pression column, spring support means for. vertically supporting, the upperend. portion. ofsaid column and the. vibration generator, and. meansfor acousticallycoupli the lower. end portion of said compression columnto the oil bearing formation.

6. The subject matter of claim 5, wherein said compression column comprises a. plurality of rod sections of progressively .increasing. cross-sectional area. in adownward. direction.

'7. The. subject matter of. claiml, wherein a plurality. of said elastic. wave generators operable at different. wave frequencies comprise the. column vibrating. means- ALBERT G. BODINE, JR.

References Cited in the. file of this patent UNITED STATES PATENTS Number Name Date Re. 23,381 Bodine June 26, 1951 1,380,869 Fay June 7,1921 2,644,807 Noyes June 23, 1936 2,056,513 Gambarine- Oct'. 6, 1936 2,089,983" Rick'er Aug; 17,193? 2,184,809 'Brammer Dec. 26, 1939 2,437,456 Bodine, Jr. Mar. 9, 1948 2,481,068" Best Sept. 6, I949 FOREIGN PATENTS Numberv Country Date 146,436 GreatBritain'nuu Nov. 25, 1920 OTHER REFERENCES Daniel1,,. Text Book-of the Principles of Physics, 1.884, pages 74-80, 82. 

